CN111644196B

CN111644196B - High-selectivity preparation method of methylpentamethylenediamine by adopting composite catalytic system

Info

Publication number: CN111644196B
Application number: CN202010554488.8A
Authority: CN
Inventors: 陈国华; 郭文杰; 赵新明
Original assignee: Shandong Damin Chemical Co ltd
Current assignee: Shandong Damin Chemical Co ltd
Priority date: 2020-06-17
Filing date: 2020-06-17
Publication date: 2021-02-09
Anticipated expiration: 2040-06-17
Also published as: CN111644196A

Abstract

The invention relates to a high-selectivity composite catalyst for preparing 2-methyl pentanediamine by hydrogenating 2-methyl glutaronitrile and a method for preparing 2-methyl pentanediamine. The method adopts a composite catalyst system which comprises a modified supported Ni/Co main catalyst and a doped silicon-aluminum-based molecular sieve secondary catalyst serving as a catalysis-assisting system. In the presence of a main catalyst containing multiple catalytic active centers and a doped modified molecular sieve cocatalyst, the hydrogenation reaction can be carried out under the hydrogen condition of less than 2MPa, with lower content of alkaline auxiliary agent and mild reaction condition, and the selectivity of the target product 2-methyl pentanediamine is not lower than 80%.

Description

High-selectivity preparation method of methylpentamethylenediamine by adopting composite catalytic system

Technical Field

The invention belongs to the field of catalytic synthesis, and particularly relates to a catalyst for synthesizing 2-methyl pentanediamine and a catalytic hydrogenation method.

Background

2-methyl-1, 5-pentanediamine is an important industrial raw material, is commonly used as a chain extender in the production of spandex and aramid fiber or as an epoxy resin curing agent, is used for preparing polyamide by wholly or partially replacing hexanediamine, can also be used as a raw material for preparing beta-picoline, and is used for preparing nicotinamide by taking the picoline as an intermediate. The small-scale preparation method comprises the steps of taking glutaronitrile as a raw material, adopting a liquid phase reaction, boiling an absolute ethyl alcohol solution of the glutaronitrile, taking metal sodium as a reducing agent, distilling by using steam after the reaction is finished, neutralizing a distillate by using dilute hydrochloric acid, washing, and distilling under reduced pressure to obtain a product, namely the pentanediamine.

In the prior art, for the industrial preparation of 2-methyl-1, 5-pentanediamine, the methylglutaronitrile is converted into methylpentanediamine by hydrogenation under high pressure in the presence of a catalyst such as Raney cobalt or Raney nickel. However, the method has poor selectivity, more than 20% of 3-methylpiperidine by-products and other by-products are generated, and the selectivity of the methylpentanediamine is not more than 80% even under the high-pressure hydrogen atmosphere (2.8-17.2 MPa) and under the premise of higher content of alkaline auxiliary substances. For example, patent US4885391 proposes a process for the hydroconversion of pure methylglutaronitrile into methylpentamethylenediamine in the presence of chromium-doped raney cobalt, although the conversion of the reaction feed MGN is substantially complete, but the MPMD selectivity of the pentanediamine product is only 70.8%, and the optimum conversion for the reaction is less than 80%; due to the excessive temperatures and reaction pressures, about 10% of unusable heavy products are also produced (although the 3-methylpiperidine by-product has some industrial applications, it is troublesome for the work-up separation operation).

Patent CN101990532/WO2009121704 discloses a preparation method of 2-methyl pentanediamine, which is based on a nickel and chromium doped Raney cobalt catalyst and is prepared by carrying out catalytic hydrogenation on 2-methyl glutaronitrile under the conditions of less than 5.0MPa of absolute hydrogen pressure, 60-160 ℃ of temperature and existence of strong alkaline inorganic compounds. Although the condition of strong alkaline inorganic compound is adopted, the reaction raw material can be completely converted, the selectivity of the methyl pentanediamine product is not over 80 percent; for dinitrile mixture feed, MGN conversion was complete, but product selectivity was only 64% due to impurity interference. CN201110309196 relates to a preparation method of 2-methyl-1, 5-pentanediamine, which is characterized in that: the method takes 2-methyl-1, 5-glutaronitrile as a raw material and a Co-Mo/gamma-Al 2O3 catalyst as a catalyst, the reaction is carried out in a gas phase, a continuous process is adopted, and the specific operation conditions are as follows: normal pressure to 10MPa, temperature: 100-320 ℃, mol ratio of cyanamide: 1.0-8.0, 2-methyl-1, 5-glutaronitrile is fed into a preheater, mixed with ammonia gas and hydrogen gas for preheating and vaporization, and then fed into a fixed bed reactor for reaction, and after the reaction, the material is subjected to condensation cooling and gas-liquid separation, and then fed into a rectification refining process; however, the reaction is a gas phase reaction, and 2-methyl-1, 5-glutaronitrile needs to be heated to be gasified into a gaseous raw material, so that the energy consumption is high; further, since the molar ratio of cyanamide is relatively high, it is difficult to separate a large amount of ammonia gas from the remaining hydrogen gas after the reaction, and it is difficult to control the molar ratio of cyanamide and the molar ratio of hydrocyanic acid stably when they are recovered and used together in practice. Further, the most significant problem of this patent is that it is suitable only for high-temperature reaction, and the gaseous starting material of 2-methyl-1, 5-glutaronitrile used therein is easily liquefied rapidly at low temperature (for example, 100 to 200 ℃), and in fact, a reaction state in which gas phase and liquid-gas phase are mixed is easily caused in a reactor, and a heterogeneous reaction is caused, which seriously affects the reaction efficiency, and it is difficult to achieve high-efficiency production in industrial operation. CN201710649791 discloses a method for preparing 2-methyl pentanediamine and 3-methyl piperidine by hydrogenating 2-methyl glutaronitrile, which relates to the steps of diluting 2-methyl glutaronitrile by a solvent in the presence of an alkaline cocatalyst in the presence of a Raney nickel catalyst doped with Fe, Cr and Yb, and obtaining 2-methyl pentanediamine and 3-methyl piperidine after hydrogenation reaction, wherein the higher total yield of the 2-methyl pentanediamine and the 3-methyl piperidine can be realized under the milder hydrogenation reaction condition. Although the patent can completely hydro-convert 2-methylglutaronitrile and the total yield of 2-methylglutaronitrile and 3-methylpiperidine is high, thereby reducing the formation of heavies or high boilers of lower economic value, the selectivity of 2-methylglutaronitrile is not significantly improved due to the lower reaction temperature and the low single selectivity of the catalyst.

Thus, in order to obtain an increase in the selectivity of 2-methylpentanediamine, it is necessary to further improve the existing raney nickel/cobalt catalyst systems and to find new catalyst systems which provide high conversion of dinitriles in order to more efficiently hydrogenate 2-methylglutaronitrile to 2-methylpentanediamine and to carry out the hydrogenation under mild conditions or milder operating conditions than those described in the prior art.

Disclosure of Invention

One of the technical problems to be solved by the invention is to overcome the defects of high temperature, low raw material conversion rate and poor diamine selectivity in the process for producing 2-methyl pentanediamine from 2-methyl glutaronitrile in the prior art, so that the selectivity of the 2-methyl pentanediamine is high, the selectivity of byproducts such as 3-methyl piperidine is low, and the production energy consumption is greatly reduced by reducing the reaction time and the reaction temperature.

The invention aims to solve another technical problem of overcoming the defects of low catalytic efficiency and poor diamine selectivity of a catalyst used for producing 2-methyl pentanediamine in the prior art, and obtains a high-yield 2-methyl pentanediamine product at a lower ammonia usage amount and a relatively mild reaction temperature by providing a specific multi-active-center catalyst and a cocatalyst; compared with the prior art, no extra alkali test is needed to be added in the reaction processAgents or alkaline solvents, passing only small amounts of ammonia or NH₃The occurrence of side reactions can be effectively inhibited.

The present invention provides improved catalysts for the production of 2-methylpentanediamine from a 2-methylglutaronitrile feedstock at high selectivity or conversion, with reduced formation of 3-methylpiperidine and other impurities.

The invention also provides a method for preparing 2-methyl pentanediamine by high-selectivity hydrogenation of 2-methyl glutaronitrile, which comprises the steps of carrying out hydrogenation reaction under the relative hydrogen medium-low pressure condition of less than 5MPa, preferably less than 3MPa and with lower content of alkaline auxiliary agent and mild reaction condition in the presence of a main catalyst containing multiple catalytic activity centers and a doped modified molecular sieve auxiliary catalyst; the selectivity of the 2-methyl pentanediamine is not less than 80 percent, and is preferably not less than 85 percent.

Specifically, in a first aspect of the invention, a composite catalyst system for preparing 2-methyl pentanediamine by hydrogenating 2-methyl glutaronitrile with high selectivity is provided; the catalyst system comprises Al modified by doping a modifier₂O₃The catalyst comprises a first catalyst (also called catalyst A) based on supported Ni/Co, and a second catalyst (also called catalyst B) of a cobalt and lanthanum doping modified silicon-aluminum molecular sieve as a catalysis-promoting system, wherein the content of the second catalyst in the composite catalytic system is not less than 20 wt%, and preferably 20-50 wt%. Wherein, the modifier in the first catalyst at least comprises a rare earth metal compound, preferably one or more of rare earth metals such as cerium, samarium, yttrium and the like; in addition, optionally, the modifier can also comprise a metal Mn compound selected as a co-modifier.

In the composite catalytic system of the present invention, preferably, the first catalyst uses rare earth metal (e.g. Ce) and metal Mn as modifiers, and the co-current precipitation method and the surface coating method are used for the rare earth metal salt and the Mn salt to react with Al₂O₃The supported Ni/Co-based multi-active center catalyst A is modified. Illustratively, in the reaction, the shaped first catalyst is in the form of a rod, preferably having a diameter of 0.5 to 1.5mm and a length of 1 to 3 mm.

In the composite catalytic system, the second catalyst is a small-particle-size hydrogen type silicon-aluminum-based molecular sieve catalyst; preferably, the molecular sieve catalyst also supports a nickel active component; more preferably, the catalyst after molding is in the form of pellets having a particle size of 0.5mm or less.

By adopting the composite catalytic system, the 2-methylglutaronitrile can be subjected to liquid-phase catalysis hydrogenation in an autoclave type reactor or a tubular reactor under the conditions of low temperature and no additional alkaline reagent (only low ammonia content is adopted, and the mass fraction of ammonia in a raw material solution is less than 0.5 wt%) so as to prepare the 2-methylglutaronitrile with high selectivity. Wherein the reaction temperature is lower than 150 ℃, preferably 80-150 ℃ (when the reaction temperature is lower than 80 ℃, the reaction efficiency is lower, the selectivity is reduced), and more preferably 80-120 ℃; the pressure of the hydrogenation reaction can be 0.5-5MPa, preferably 0.5-2 MPa.

Preferably, the hydrogenation reaction is carried out in a liquid medium.

Specifically, the invention also provides a preparation method of the first catalyst (catalyst A), which comprises the following specific preparation steps:

s1, preparing a solution from the mixture of aluminum nitrate and nickel nitrate/cobalt nitrate by using deionized water, stirring and heating the solution to 70-80 ℃ in a reaction kettle with stirring and heating functions, wherein the mass ratio of the aluminum nitrate to the mixture of nickel nitrate/cobalt nitrate is 2-10:1, and the mass ratio of the nickel nitrate to the cobalt nitrate is 1-3: 1;

dropwise adding 15-30 wt% of ammonia water solution under the conditions of keeping constant temperature and stirring until the pH value of the solution is stable at 8-9 (preferably 8-8.5), continuously stirring for precipitation after dropwise adding is finished, then transferring to a crystallization kettle for static crystallization for 1-2h, filtering, washing, drying and crushing a filter cake, adding sesbania powder and optional other forming aids, extruding or tabletting for forming (for example, extrusion molding by using a circular orifice plate with the outer diameter of 0.5-1.5 mm), and then roasting in a muffle furnace at 550-600 ℃ for 4-6h to obtain a catalyst intermediate.

S2 weighing appropriate CoCl₂Or dissolving the hydrate in deionized water, mixing with the aqueous solution of rare earth metal salt uniformly to obtain a steeping liquor, and steeping the catalyst intermediate for 2-3h by an isometric steeping method at 70-80 ℃ under the stirring condition; drying after impregnationObtaining a catalyst semi-finished product; wherein, CoCl₂The mass amount of the rare earth metal salt is 5-20 wt% of the aluminum nitrate, and the mass amount of the rare earth metal salt is 1-5 wt% of the aluminum nitrate;

illustratively, the aqueous rare earth metal salt solution may be, for example, 50 wt% cerium nitrate or yttrium nitrate.

Optionally, the rare earth metal salt can also be selected from one or a mixture of more than two of lanthanum nitrate, lanthanum carbonate and cerium carbonate.

S3, uniformly spraying a manganese nitrate solution serving as a second auxiliary agent on the semi-finished catalyst, keeping the semi-finished catalyst in a rolling or mixing state in the spraying process, drying after spraying, and roasting at 450-500 ℃ for 4-5 hours in a nitrogen atmosphere to obtain a catalyst precursor; wherein the concentration of the manganese nitrate solution can be 20-50g/L, and the mass amount of the manganese nitrate is 0.1-1 wt% of that of the aluminum nitrate;

and (3) continuously roasting the roasted catalyst precursor in a nitrogen-hydrogen mixed atmosphere containing 20-30% by volume of hydrogen at the temperature of 380-450 ℃ for 2-3h to obtain a catalyst finished product.

The basic carrier of the first catalyst prepared by the invention is alumina, the doped active element is Ni/Co, and rare earth metal and metal manganese are used for modification; in a preferred embodiment, the diameter of the obtained finished catalyst is 0.5-1.5mm, the average pore diameter is not more than 10nm, and the average pore volume is 0.4-0.6 ml/g. Compared with a Raney nickel catalyst, the catalyst can effectively inhibit side reactions without adding an additional alkaline reagent or solvent, has a simple post-reaction treatment process and mild reaction conditions, and can obtain higher conversion rate and target product selectivity by matching with a cocatalyst system. In some preferred embodiments, the conversion of the starting material is substantially 100% and the diamine selectivity is up to 90% or more.

Illustratively, the specific preparation steps of the first catalyst are as follows.

1) Weighing 70-90g of aluminum nitrate and 10-30g of nickel nitrate/cobalt nitrate (the weight ratio of nickel nitrate/cobalt nitrate is 1-2:1), adding deionized water to prepare 200mL of solution, pouring the solution into a glass reaction kettle with stirring and heating, heating to 70-80 ℃, dropwise adding 15-30 wt% of ammonia water solution under the conditions of constant temperature and stirring until the pH value of the solution is 8-8.5, continuously stirring for 10-15min after dropwise adding is finished, precipitating, and then transferring to a crystallization kettle for static crystallization for 1-2 h; filtering, washing with deionized water and methanol, drying at 110 deg.C for 10-12 hr, oven drying the filter cake, pulverizing, adding magnesium stearate 0.1-0.2g and sesbania powder 0.5-1g, extrusion molding (extrusion molding with circular orifice plate with outer diameter of 0.5-1.5 mm), and calcining at 550-600 deg.C in muffle furnace for 4-6 hr to obtain catalyst intermediate.

2) Weighing 8-10g CoCl₂Dissolving 4H2O in 100ml of deionized water, uniformly mixing with 4-6g of rare earth metal salt aqueous solution (50 wt% of cerium nitrate or yttrium nitrate) to obtain an impregnation solution, and impregnating the catalyst intermediate for 2-3 hours at 70-80 ℃ under the stirring condition; and drying after the impregnation is finished to obtain a semi-finished catalyst.

3) Uniformly spraying 10mL of 30-50mg/mL manganese nitrate solution serving as a second auxiliary agent on the semi-finished catalyst product, drying at 120 ℃ after spraying, and roasting at 450-500 ℃ in a nitrogen atmosphere for 4-5h to obtain a catalyst precursor; and (3) continuously roasting the roasted catalyst precursor in a nitrogen-hydrogen mixed atmosphere containing 20-30% by volume of hydrogen at 400 ℃ for 2-3h to obtain a catalyst finished product.

The invention also provides a preparation method of the second catalyst, which comprises the following specific preparation steps:

s1, weighing a proper amount of cobalt nitrate hexahydrate, lanthanum nitrate and an organic template agent, sequentially adding the cobalt nitrate hexahydrate, the lanthanum nitrate and the organic template agent into 1-2 wt% of sodium hydroxide solution, and stirring and mixing for 5-10min to be uniform; adding aluminum hydroxide powder into the solution at room temperature, rapidly stirring, adding 30-40 wt% of silica sol, continuously and rapidly stirring for 10-15min, then adding mesoporous silica with the particle size of less than 50nm, continuously stirring, slowly adding n-propylamine, and stirring for 2-3h to obtain gel;

wherein the mass ratio of cobalt nitrate to lanthanum nitrate to the template to aluminum hydroxide is 1-2: 0.1-0.5: 50-100: 5-10;

wherein the mass ratio of the aluminum hydroxide, the silica sol and the mesoporous silica particles is 5-10: 200-300: 30-50, wherein the mass usage amount of the n-propylamine is 1-5 times of that of the aluminum hydroxide;

s2, adding the uniformly stirred solution into a crystallization kettle, dynamically crystallizing for 24 hours at the temperature of 160-165 ℃ at the speed of 50-80 rpm, then heating to 170-180 ℃, and maintaining the temperature to perform static crystallization for 48-60 hours;

s3, preliminary calcination: after crystallization, taking out the inner container of the crystallization kettle, quickly cooling to 15-20 ℃ in an ice water bath, centrifuging to obtain a product, washing the product to be neutral by using deionized water, drying, and calcining at 550-580 ℃ for 6-8h in a muffle furnace to obtain molecular sieve raw powder;

secondary calcination: soaking the primary calcined raw powder in 0.5-1mol/L ammonium nitrate solution, controlling the solid-liquid ratio to be 1:20-30, slowly stirring at 70-80 ℃ for 1.5-2h, filtering, and washing; repeating the soaking-washing operation for three times, drying the sample, and calcining the sample in a muffle furnace at 550-580 ℃ for 4-5h to obtain the cobalt and lanthanum doped modified silicon-aluminum-based molecular sieve powder.

S4, molding treatment: mixing the molecular sieve powder and boehmite according to a weight ratio of 5:0.1-1, adding a proper amount of polyvinyl alcohol or carboxymethyl cellulose, wetting with deionized water, tabletting and forming, fully drying at 110-120 ℃, crushing, sieving, selecting a molecular sieve with the particle size of 0.1-0.5mm, roasting at 550 ℃ for 3-5h to obtain formed molecular sieve particles with the average particle size of less than 0.5mm, and using the formed molecular sieve particles as a second catalyst.

Wherein the dosage of the polyvinyl alcohol or the carboxymethyl cellulose is 1 to 3 weight percent of the molecular sieve powder; the dosage of the deionized water is 0.3-0.4 times of the weight of the molecular sieve powder.

Preferably, the molecular sieve second catalyst further comprises a post-impregnation treatment step, which is as follows:

soaking the prepared molecular sieve particles in 2-3 wt% nickel nitrate solution with the same volume for 2-5h at room temperature, then heating to evaporate water and fully drying at 100-110 ℃, and then calcining the dried solid again: firstly calcining at 400-450 ℃ for 2h, then naturally cooling to room temperature, then calcining at 350-360 ℃ for 1-2h in hydrogen atmosphere, and naturally cooling to room temperature to prepare the second catalyst containing the supported nickel.

Illustratively, the preparation steps of the second catalyst are as follows.

1) Weighing 1-2g of cobalt nitrate hexahydrate, 0.1-0.3g of lanthanum nitrate and 80-100g of template agent TBABr, sequentially adding the materials into 1000ml of 1-1.5 wt% sodium hydroxide solution, and stirring and mixing for 5-10min until the materials are uniform; adding 5-10g of aluminum hydroxide into the solution at room temperature, and quickly stirring for 10-15 minutes; then adding 250-300g of 30-40% silica sol, continuously and rapidly stirring for 10-15min, adding 30-45g of solid mesoporous silica microspheres with the particle size of 20-50nm as a supplementary silicon source and a crystal promoter, continuously stirring, slowly adding 10-12g of n-propylamine after stirring for 10min, and stirring for 2-3h to obtain a gel solution; adding the uniformly stirred solution into a crystallization kettle with a polytetrafluoroethylene lining, dynamically crystallizing for 24 hours at 160-165 ℃ at 50-80 rpm, then heating to 170-180 ℃, and maintaining the temperature to perform static crystallization for 48-60 hours;

2) after crystallization is finished, taking out the inner container of the crystallization kettle, quickly cooling to 15-20 ℃ in ice water bath, centrifuging to obtain a product, washing the product to be neutral by using deionized water, drying and drying to obtain a sample; the dried sample is heated to 550-580 ℃ at the speed of 1-5 ℃/min in a muffle furnace and is calcined for 6-8h at high temperature; thus obtaining the cobalt and lanthanum doping modified silicon-aluminum based molecular sieve raw powder. Soaking the raw powder in 0.5-1mol/L ammonium nitrate solution, controlling the solid-liquid ratio to be 1:20-30, slowly stirring at 70-80 ℃ for 1.5-2h, performing suction filtration and washing, repeating the soaking-washing operation for three times, and drying; and calcining the dried sample in a muffle furnace at 550-580 ℃ for 4-5h to obtain a cobalt and lanthanum doped modified silicon-aluminum based molecular sieve powder product.

3) Mixing the prepared molecular sieve powder and boehmite according to the weight ratio of 5:0.1-1, adding a proper amount of polyvinyl alcohol, wetting by deionized water with the weight of 0.3-0.4 times, tabletting and forming, fully drying at 110-120 ℃, crushing, sieving, selecting a molecular sieve with the particle size of about 0.2-0.5mm, and roasting at 550 ℃ for 3-5 hours to obtain formed molecular sieve particles.

4) Soaking the prepared molecular sieve in 2-3 wt% nickel nitrate solution at room temperature for 2 hr, evaporating water, drying at 100-110 deg.C, and dryingSecondary calcination: calcining at 400-450 deg.C for 2 hr, naturally cooling to room temperature, and calcining in H₂Calcining for 1h at 350-360 ℃ in the atmosphere, and naturally cooling to room temperature to prepare the nickel-loaded molecular sieve serving as a second catalyst.

The second catalyst of the molecular sieve prepared by the method has small particle size and large specific surface area (generally 300-500 m)²A/g, far exceeding 80-150m of the first catalyst²/g), excellent molecular diffusion performance, high diamine product selectivity and controllable particle size; when the catalyst is used in a tubular reactor, the catalyst can be effectively filled between larger gaps formed by the first catalyst, and the contact area between the catalyst and reaction molecules is increased. In addition, through multiple calcination operations, multiple active metal centers can be firmly introduced into the inner surface and the outer surface of the molecular sieve pore channel; and the introduction of the mesoporous silica microsphere particles enables the molecular sieve to have a micropore-mesoporous composite pore structure, further expands the pore structure type of the molecular sieve and obviously improves the reaction speed.

Compared with a Raney nickel catalyst, the two catalysts A, B are matched and cooperated with each other, so that the composite catalytic system has multiple active metal centers and auxiliary components such as rare earth metals and metal Mn with improved selectivity, side reactions can be effectively reduced even under low ammonia consumption, particularly the distribution of active centers in the interior and on the surface of the catalyst is effectively improved by using a modification auxiliary agent of a specific metal, and the selectivity of a target product is improved.

Preferably, the composite catalyst of the invention is subjected to calcination pretreatment before use, and the method comprises the following steps: heating the catalyst to 350-360 ℃ in a hydrogen atmosphere, maintaining the hydrogen atmosphere for heat preservation treatment for a period of time, such as 3-10 hours, after the temperature is constant.

In another aspect, the present invention also provides the use of the above composite catalyst, namely: the method for preparing 2-methyl pentanediamine by hydrogenating 2-methyl glutaronitrile in the presence of the catalyst comprises the following specific scheme:

in the presence of the composite catalyst or the pretreated composite catalyst, 2-methylglutaronitrile is catalyzed to carry out hydrogenation reaction in an autoclave type reactor containing an alcohol solvent under the conditions of 80-120 ℃, the presence of low-content ammonia and 0.5-5MPa of hydrogen pressure, so that the target product 2-methylglutaronitrile is prepared with high selectivity.

Wherein, the alcohol solvent is preferably methanol or ethanol, and the water content is lower than 5%; the low content ammonia is: the ammonia content of the solution is less than 0.5 wt%.

Illustratively, the preferred operational procedure is: adding an alcohol solvent and the purified raw material 2-methylglutaronitrile (the purity is not lower than 99%) into a high-pressure reaction kettle, uniformly stirring, adding an ammonia water solution with the weight percent of 20-30% to ensure that the ammonia content is 0.1-0.5% of the solution, and then adding a catalyst to 1-10% by weight; replacing the internal atmosphere of the reaction kettle with hydrogen, stirring and reacting at the hydrogen pressure of 0.5-3MPa and the reaction temperature of 80-120 ℃, keeping the temperature and the pressure constant in the reaction process, taking the hydrogen absorption stop as a reaction terminal point, carrying out HPLC (high performance liquid chromatography) chromatographic analysis on a product solution, and determining the conversion rate of the raw materials and the content of the 2-methylpentanediamine product.

Alternatively, the following preparation scheme may also be employed.

Adding a proper amount of composite catalyst into a fixed bed reactor, continuously adding an alcohol solvent into the fixed bed reactor by using a pump to fill the fixed bed reactor, heating to the reaction temperature, adjusting the hydrogen pressure to be 0.5-5MPa, controlling the hydrogen flow (for example, to be 1-2L/min), and continuously adding an alcohol solution raw material flow containing 10-20 wt% of 2-methylglutaronitrile into the fixed bed reactor by using the pump after the temperature and the pressure are stable, wherein the alcohol solution also contains 0.1-0.5 wt% of ammonia; the solution flow rate of the feed stream is adjusted (for example, to 5 to 10mL/min), and the reaction mass is sampled and analyzed at regular time intervals. In a preferred embodiment, the conversion rate of the raw material is measured to be more than 95%, the selectivity of the 2-methyl pentanediamine is measured to be more than 85%, and the material is rectified to obtain the 2-methyl pentanediamine product.

Additionally, the composite catalyst of the present invention is also suitable for continuous hydrogenation reaction of 2-methylglutaronitrile under gas phase condition. Illustratively, the operational flow is:

a tubular reactor is adopted in the reaction section of the gas phase reaction, the screened second catalyst particles with the particle size of 0.3-0.5 mu m are mixed with the first catalyst and then filled in a reaction tube, hydrogen is introduced for replacing atmosphere before the reaction, and the catalyst is roasted and pretreated;

preheated NH is delivered by a metering pump₃、H₂Pumping the mixture into a raw material preheater according to a certain proportion, and mixing and heating to obtain a gas mixed raw material; continuously feeding or dropping metered preheated 2-methylglutaronitrile raw material (preferably glutaronitrile raw material, NH) into the upper end of the reaction tube through the feeding tube₃、H₂The molar ratio of (1: 0.1) - (1: 10-30); heating the reactor through a heating jacket attached to the reaction tube, wherein the pressure in the reactor is 0.5-5MPa, and the space velocity of the gas-phase raw material is 1-1.5h^-1；

Condensing the reaction crude product flowing out of the reactor, separating gas from liquid, compressing the gas phase to enter a raw material preheater, collecting the liquid phase, and rectifying, separating and purifying to obtain the 2-methyl pentanediamine.

The beneficial effects of the invention include but are not limited to the following aspects:

the invention adopts a catalytic system combining a multi-active center main catalyst and a supported molecular sieve cocatalyst, and expands the form of the catalyst and the pore structure type of the molecular sieve by adjusting the type selection of catalytic components and the proportion of catalytic auxiliaries, thereby having the performances of high catalytic efficiency and high selectivity.

Compared with Raney nickel/cobalt catalysts or other metal catalysts loaded by carriers, the composite catalytic system provided by the invention has the advantages that by fusing multi-active center components (such as nickel, cobalt, lanthanum and the like) with improved catalytic effect and auxiliary components such as rare earth metals and metal Mn with improved selectivity, the defect of insufficient contact between the catalyst and reaction molecules in the prior art is overcome through high-temperature sintering and curing on the basis of proper pore structure; the reaction temperature and pressure are also reduced, the occurrence of side reactions is effectively reduced under the condition of low ammonia dosage, particularly, the distribution of active centers in the catalyst and on the surface is effectively improved by using the specific metal modification auxiliary agent, and the selectivity of a target product is obviously improved.

The molecular sieve second catalyst has small particle size and large specific surface area (300-500 m)²The catalyst has the advantages of/g), the defect of insufficient molecular diffusivity caused by independently adopting the first catalyst is overcome in the reaction, the reaction time and the temperature are effectively reduced, the yield of byproducts is obviously inhibited, and particularly, the cocatalyst can be effectively filled in gaps formed by the first catalyst in the tubular reactor, so that the reaction efficiency can be greatly improved. Meanwhile, through multiple calcination operations, multiple active metal centers are firmly introduced into the interior and the surface of the molecular sieve, and the molecular sieve can be recycled for multiple times.

In the preparation of the second catalyst, the introduction of the crystal promoter-mesoporous silica microsphere particles enables the molecular sieve to have a composite micropore-mesoporous composite pore structure, expands the internal pore passage of the molecular sieve and improves the utilization rate of the internal active center site of the micropore in the composite molecular sieve crystal. In addition, in the composite catalyst, the specific modified molecular sieve cocatalyst with smaller particle size has more particles, so that the contact area between reaction molecules and active metal is increased.

Drawings

FIG. 1 is a partial view (scale of 50 nm) of a photograph of a metal particle-supporting first catalyst A1 under a transmission electron microscope in production example 1.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

The following detailed description of preferred embodiments of the invention and the examples included therein will make it easier to understand the context of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Preparation example 1

1) Weighing 76g of aluminum nitrate and 24g of nickel nitrate/cobalt nitrate mixed material (15 g of nickel nitrate and 9g of cobalt nitrate), adding deionized water to prepare 200mL of solution, pouring the solution into a glass reaction kettle with stirring and heating, heating to 70 ℃, dropwise adding 25 wt% of ammonia water solution under the conditions of constant temperature and stirring until the pH value of the solution is 8-8.5, continuously stirring for 10min after dropwise adding is finished, precipitating, and then transferring the solution into a crystallization kettle for static crystallization for 2 h; filtering, fully washing by deionized water and methanol, drying at 110 ℃ for 10h to dry a filter cake, crushing, adding 0.1g of magnesium stearate and 0.5g of sesbania powder, extruding and molding by adopting a circular orifice plate with the outer diameter of 1mm, roasting at 580 ℃ in a muffle furnace for 5h, taking out and cooling to obtain a catalyst intermediate.

2) Weighing 10g of cobalt chloride tetrahydrate, dissolving the cobalt chloride tetrahydrate in 100ml of deionized water, uniformly mixing the cobalt chloride tetrahydrate and 6g of 50 wt% of cerium nitrate solution to serve as impregnation liquid, and impregnating the catalyst intermediate for 3 hours at 70 ℃ under the stirring condition; and drying after the impregnation is finished to obtain a semi-finished catalyst.

3) Uniformly spraying 10mL of a 50mg/mL manganese nitrate solution serving as a second auxiliary agent on the semi-finished catalyst product, fully mixing while spraying, drying at 120 ℃ after spraying, and roasting at 450 ℃ for 4 hours in a nitrogen atmosphere to obtain a catalyst precursor; and (3) continuously roasting the roasted catalyst precursor in a nitrogen-hydrogen mixed atmosphere containing 30% by volume of hydrogen at 400 ℃ for 2h to obtain a first catalyst product, namely catalyst A1.

Preparation example 2

1) Weighing 82g of aluminum nitrate and 18g of nickel nitrate/cobalt nitrate mixed material (the weight ratio of nickel nitrate to cobalt nitrate is 1:1), adding deionized water to prepare 200mL of solution, pouring the solution into a glass reaction kettle with stirring and heating, heating to 75 ℃, dropwise adding 30 wt% of ammonia water solution under the conditions of constant temperature and stirring until the pH value of the solution is about 8.5, continuously stirring for 15min after dropwise adding is finished, precipitating, and then transferring the solution into a crystallization kettle for static crystallization for 1 h; filtering, washing by deionized water and methanol, drying at 110 ℃ for 12h to dry a filter cake, crushing, adding 0.2g of magnesium stearate and 1g of sesbania powder, extruding into strips by adopting a circular pore plate with the outer diameter of 1mm, and roasting at 550 ℃ in a muffle furnace for 6h to obtain a catalyst intermediate.

2) Weighing 8g of cobalt chloride tetrahydrate, dissolving the cobalt chloride tetrahydrate in 100ml of deionized water, uniformly mixing the cobalt chloride tetrahydrate and 5g of 50 wt% yttrium nitrate solution to serve as impregnation liquid, and impregnating the catalyst intermediate for 2 hours at 70 ℃ under the stirring condition; and drying after the impregnation is finished to obtain a semi-finished catalyst. And uniformly spraying 10mL of 30mg/mL manganese nitrate solution serving as a second auxiliary agent on the semi-finished catalyst product, drying at 120 ℃ after spraying, and roasting at 420 ℃ for 5 hours in a nitrogen atmosphere to obtain a catalyst precursor. And (3) continuously roasting the roasted catalyst precursor in a nitrogen-hydrogen mixed atmosphere containing 20% by volume of hydrogen at the temperature of 400 ℃ for 3 hours to obtain a first catalyst finished product, namely catalyst A2.

Preparation example 3

1) Weighing 2g of cobalt nitrate hexahydrate, 300mg of lanthanum nitrate and 80g of template TBABr, sequentially adding the cobalt nitrate hexahydrate, the 300mg of lanthanum nitrate and the 80g of template TBABr into 1000ml of 1.5 wt% sodium hydroxide solution, and stirring and mixing for 10min to be uniform; adding 10g of aluminum hydroxide into the solution at room temperature, and quickly stirring for 15 minutes; then adding 260g of 40 wt% silica sol, continuously and rapidly stirring for 10min, then adding 40g of nano mesoporous silica particles with the particle size of 20-50nm as a supplementary silicon source and a crystal promoting agent, continuously stirring, slowly adding 11g of n-propylamine after stirring for 10min, and stirring for 3h to obtain a gel solution; adding the uniformly stirred solution into a crystallization kettle with a polytetrafluoroethylene lining, dynamically crystallizing at 160-165 ℃ for 24 hours at 50 revolutions per minute, then heating to 175 ℃, and maintaining the temperature to perform static crystallization for 48 hours;

2) and after crystallization is finished, taking out the inner container of the crystallization kettle, quickly cooling to 20 ℃ in an ice-water bath, centrifuging to obtain a product, washing the product to be neutral by using deionized water, drying to obtain a dried sample, and heating the dried sample to 560 ℃ at the speed of 2-3 ℃/min in a muffle furnace for high-temperature calcination for 6 hours to obtain the cobalt and lanthanum doped modified silicon-aluminum based molecular sieve raw powder. Soaking the raw powder in 3L of 0.5mol/L ammonium nitrate solution, slowly stirring at 70 deg.C for 2 hr, filtering, washing, repeating the soaking-washing operation for three times, and oven drying; and calcining the dried sample in a muffle furnace at 550 ℃ for 4h to obtain the cobalt and lanthanum doped modified silicon-aluminum based molecular sieve powder.

3) Mixing the prepared molecular sieve powder with 15g of boehmite, adding 2g of polyvinyl alcohol, wetting with 55ml of deionized water, tabletting and forming, fully drying at 110 ℃ after forming, crushing, sieving, and roasting molecular sieve particles with the particle size of 0.2-0.4mm at 550 ℃ for 5 hours to obtain formed molecular sieve particles.

4) 50g of the molecular sieve prepared above was taken and immersed in 50ml of a 3 wt% nickel nitrate solution at room temperature for 2h, followed by evaporation of water and thorough drying at 110 ℃, and then the dried solid was calcined again: firstly calcining at 450 ℃ for 2H, then naturally cooling to room temperature, then calcining at 360 ℃ for 1H under the atmosphere of H2, and naturally cooling to room temperature to prepare about 50g of the nickel-loaded cobalt and lanthanum doped modified molecular sieve serving as a second catalyst, namely catalyst B1. The average particle diameter of the molecular sieve particles is less than 0.5mm, and the specific surface area is 450-480m²/g。

Preparation example 4

1) Weighing 1g of cobalt nitrate hexahydrate, 0.2g of lanthanum nitrate and 80g of template TBABr, sequentially adding the cobalt nitrate hexahydrate, the lanthanum nitrate and the template TBABr into 1000ml of 1.5 wt% sodium hydroxide solution, and stirring and mixing for 5min to be uniform; adding 6g of aluminum hydroxide into the solution at room temperature, and quickly stirring for 10 min; then adding 300g of 40 wt% silica sol, continuing to stir rapidly for 10min, then adding 30g of solid mesoporous silica microspheres with the particle size of 20-50nm as a supplementary silicon source and a crystal promoter, continuing to stir, slowly adding 10g of n-propylamine after stirring for 10min, and stirring for 2.5h to obtain a gel solution; adding the uniformly stirred solution into a crystallization kettle with a polytetrafluoroethylene lining, dynamically crystallizing at 160 ℃ for 24 hours at a speed of 80 revolutions per minute, then heating to 180 ℃, and maintaining the temperature to perform static crystallization for 60 hours;

2) after crystallization is finished, taking out the inner container of the crystallization kettle, quickly cooling to 15 ℃ in ice water bath, centrifuging to obtain a product, washing the product to be neutral by using deionized water, drying and drying to obtain a sample; and (3) heating the dried sample to 550 ℃ at the speed of 3 ℃/min in a muffle furnace, and calcining at high temperature for 6h to obtain the cobalt and lanthanum doped modified silicon-aluminum based molecular sieve raw powder. Soaking the raw powder in 3.6L of 1mol/L ammonium nitrate solution, slowly stirring at 70 deg.C for 1.5h, filtering, washing, repeating the soaking-washing operation for three times, and oven drying; and calcining the dried sample in a muffle furnace at 580 ℃ for 4h to obtain a cobalt and lanthanum doped modified silicon-aluminum based molecular sieve powder product.

3) Mixing 100g of the prepared molecular sieve powder with 12g of boehmite, adding 1.8g of polyvinyl alcohol, wetting with 40ml of deionized water, tabletting and forming, fully drying at 120 ℃, crushing, sieving, selecting a molecular sieve with the particle size of 0.4-0.5mm, roasting at 550 ℃ for 5 hours to obtain formed molecular sieve particles, calcining at 350 ℃ for 1 hour in the atmosphere of H2, and naturally cooling to room temperature to obtain the unsupported cobalt-lanthanum doped modified silicon-aluminum-based molecular sieve which is marked as a catalyst B2.

Example 1

The mixed catalyst A1 and catalyst B1 are used as a composite catalyst system A1/B1, wherein the content of the catalyst A1 in the composite catalyst system is 55 wt%, and the content of the catalyst B1 in the composite catalyst system is 45 wt%.

1) Adding the following raw materials into a high-pressure closed reaction kettle: 25g of rectified 2-methylglutaronitrile (HPLC purity is more than 99.5%), 150ml of absolute ethyl alcohol, 1ml of 25 wt% ammonia water, and 5g of the composite catalyst A1/B1;

2) sealing the reaction kettle after the feeding is finished, purging the reaction kettle for a plurality of times by using hydrogen to replace the air atmosphere in the kettle, filling 1.8MPa hydrogen into the reaction kettle, heating the reaction kettle to the reaction temperature of 100 ℃, and starting stirring (the stirring speed is 550rpm) to carry out reaction; the reaction was carried out under conditions of maintaining the reaction temperature at 100 ℃ and the reaction pressure at 1.8MPa, indicating the end of the reaction when hydrogen was no longer consumed.

3) After the reaction is finished, measuring the reaction time for 48 min; the product solution was collected and analyzed by liquid chromatography, and the results indicated that the conversion of the starting material was essentially 100%, indicating that the conversion of the starting material was essentially complete, with a selectivity of about 91.6% for 2-methylpentamethylenediamine and a total selectivity of about 10.3% for impurities.

Example 2

The reaction was carried out according to the procedure of example 1; the difference is that: in the composite catalyst system A1/B1, the weight of catalyst A1 is 60 percent, and the weight of catalyst B1 is 40 percent; the reaction temperature was 120 ℃.

The reaction time is 45 min; the liquid chromatographic analysis of the product shows that the conversion rate of the raw material is 100 percent, which shows that the conversion of the raw material is complete and the selectivity of the target product 2-methyl pentanediamine is 92.7 percent.

Example 3

The hydrogenation was carried out as in example 1; the difference is that: the reaction solvent was anhydrous methanol (instead of ethanol in example 1); the reaction pressure is 1.5MPa, and the reaction temperature is 90 ℃.

The result shows that the reaction time is 55min when the raw material conversion is complete; product chromatography showed 2-methylpentamethylenediamine selectivity to be about 90.2%.

Example 4

The hydrogenation was carried out as in example 1; the difference is that: the composite catalyst system is A2/B2, wherein the weight of the catalyst A2 is 55 percent, and the weight of the catalyst B2 is 45 percent; the reaction temperature was 85 ℃.

The result shows that the reaction time is 58min when the raw material conversion is complete; product chromatography showed a selectivity for 2-methylpentamethylenediamine of 89.3%.

Example 5

A composite catalyst system A1/B1 (wherein the catalyst A1 is 50 wt% and the catalyst B1 is 50 wt%) was charged into a fixed bed reactor. Continuously adding an ethanol solvent into a fixed bed reactor by using a pump to fill the fixed bed reactor, and adjusting the hydrogen pressure to be 3MPa and the hydrogen flow to be 2L/min; heating to 80 ℃, and after the temperature and the pressure are stable, continuously adding the preheated ethanol solution raw material flow containing 15 wt% of 2-methylglutaronitrile into the fixed bed reactor by using a pump, wherein the raw material flow also contains 0.18 wt% of ammonia; adjusting the flow rate of the raw material flow to 10mL/min in the reaction process, and sampling and analyzing the reaction materials at regular time; after a running time of 15h, the conversion of the 2-methylglutaronitrile starting material was found to be 95.3% and the selectivity of the product, 2-methylpentanediamine, was found to be 88.4%.

Comparative example 1

The hydrogenation was carried out as in example 1; the difference is that: the reaction temperature was 70 ℃.

The result shows that the reaction time is 96 min; liquid chromatography analysis shows that the selectivity of the target product 2-methyl pentanediamine is 84.9%.

Comparative example 2

The hydrogenation was carried out as in example 1; the difference is that: the reaction temperature was 50 ℃.

The result shows that the reaction time is 122 min; liquid chromatography analysis shows that the selectivity of the target product 2-methyl pentanediamine is 76.2%.

Comparative example 3

The hydrogenation was carried out as in example 1; the difference is that: the reaction temperature is 70 ℃; in the composite catalyst system A1/B1, the weight percent of catalyst A1 is 95 percent and the weight percent of catalyst B1 is 5 percent. Liquid chromatography analysis shows that the selectivity of the target product 2-methyl pentanediamine after the reaction is finished is 81.7%.

Comparative example 4

The hydrogenation was carried out as in example 1; the difference is that: the reaction temperature is 70 ℃; in the composite catalyst system A1/B1, the weight of catalyst A1 is 5 wt%, and the weight of catalyst B1 is 95 wt%. Liquid chromatography analysis shows that the selectivity of the target product 2-methyl pentanediamine is 75.8% after the reaction is finished.

Comparative example 5

The hydrogenation was carried out as in example 1; except that only a molecular sieve co-catalyst was employed, namely: in the composite catalyst system A1/B1, the weight of catalyst A1 is 0 wt%, and the weight of catalyst B1 is 100 wt%. Liquid chromatography analysis shows that the selectivity of the target product 2-methyl pentanediamine after the reaction is finished is 68.4%.

From the above examples and comparative examples, it can be seen that, by using the specific composite catalytic system with multiple catalytic active centers of the present invention, under the conditions of relatively low ammonia content, hydrogen pressure and relatively mild hydrogenation reaction, complete conversion of 2-methylglutaronitrile can be achieved within a relatively short reaction time, and relatively high selectivity of 2-methylglutaronitrile can be achieved; additionally, the lower ammonia content and mild reaction conditions also effectively suppress the formation of by-products.

Although the present invention has been described in detail by referring to the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention.

Claims

1. Composite catalyst for preparing 2-methyl pentanediamine from 2-methyl glutaronitrile at high selectivity, wherein the composite catalyst comprises modified Al₂O₃The catalyst comprises a first supported Ni/Co-based catalyst and a second catalyst of a cobalt and lanthanum Co-doped silicon-aluminum-based molecular sieve as a cocatalyst; the method is characterized in that the content of the second catalyst in the composite catalyst is 20-50 wt%; wherein the modifier for the first catalyst modification comprises at least one rare earth metal compound; wherein the rare earth metal is selected from one or more of cerium, samarium and yttrium, and the modifier also comprises a manganese metal compound.

2. The composite catalyst of claim 1, wherein the second catalyst is further supported with metallic nickel.

3. The composite catalyst of claim 1 or 2, wherein the first catalyst is prepared by:

s1: preparing a solution from a mixture of aluminum nitrate and nickel nitrate/cobalt nitrate by using deionized water, stirring and heating the solution to 70-80 ℃ in a reaction kettle with stirring and heating functions, wherein the mass ratio of the aluminum nitrate to the mixture of the nickel nitrate/cobalt nitrate is 2-10:1, and the mass ratio of the nickel nitrate to the cobalt nitrate is 1-3: 1; dropwise adding 15-30 wt% of ammonia water solution under the conditions of constant temperature and stirring until the pH value of the solution is 8-9, continuously stirring for precipitation after dropwise adding is finished, then transferring to a crystallization kettle for static crystallization for 1-2h, filtering, washing, drying and crushing a filter cake, adding a forming auxiliary agent, extruding or tabletting for forming, and then roasting in a muffle furnace at 550-600 ℃ for 4-6h to obtain a catalyst intermediate;

s2: weighing appropriate amount of CoCl₂Dissolving in deionized water, mixing with rare earth metal salt water solution uniformly to obtain a soaking solution, and soaking the catalyst intermediate for 2-3h at 70-80 ℃ under stirring; drying after the impregnation is finished to obtain a semi-finished catalyst product; wherein, CoCl₂The mass amount of the rare earth metal salt is 5-20 wt% of the aluminum nitrate, and the mass amount of the rare earth metal salt is 1-5 wt% of the aluminum nitrate;

s3: uniformly spraying a manganese nitrate solution serving as a second auxiliary agent on the semi-finished catalyst, drying after spraying, and roasting at 450-500 ℃ for 4-5h in a nitrogen atmosphere to obtain a catalyst precursor, wherein the mass amount of the manganese nitrate is 0.1-1 wt% of that of the aluminum nitrate; and (3) continuously roasting the roasted catalyst precursor for 2-3h at 380-450 ℃ in a nitrogen-hydrogen mixed atmosphere containing 20-30% of hydrogen by volume fraction to obtain a first catalyst finished product.

4. The composite catalyst of claim 1 or 2, wherein the second catalyst is prepared by:

s1: weighing a proper amount of cobalt nitrate, lanthanum nitrate and an organic template agent, sequentially adding the cobalt nitrate, the lanthanum nitrate and the organic template agent into a 1-2 wt% of sodium hydroxide solution, and stirring the mixture uniformly; adding aluminum hydroxide powder into the solution at room temperature, rapidly stirring, adding 30-40 wt% of silica sol, continuously and rapidly stirring, then adding mesoporous silica with the particle size of less than 50nm, continuously stirring, slowly adding n-propylamine, and stirring for 2-3h to obtain gel;

wherein the mass ratio of the aluminum hydroxide, the silica sol and the mesoporous silica particles is 5-10: 200-300: 30-50, wherein the mass amount of the n-propylamine is 1-5 times of that of the aluminum hydroxide;

s2: adding the uniformly stirred solution into a crystallization kettle, dynamically crystallizing at 160-165 ℃ for 24 hours at 50-80 rpm, then heating to 170-180 ℃, and maintaining the temperature to perform static crystallization for 48-60 hours;

s3: after crystallization, taking out the inner container of the crystallization kettle, quickly cooling to 15-20 ℃ in an ice water bath, centrifuging to obtain a product, washing the product to be neutral by using deionized water, drying, and calcining at 550-580 ℃ for 6-8h in a muffle furnace to obtain molecular sieve raw powder;

soaking the primary calcined raw powder in 0.5-1mol/L ammonium nitrate solution, controlling the solid-liquid ratio to be 1:20-30, slowly stirring at 70-80 ℃ for 1.5-2h, filtering, and washing; repeating the soaking-washing operation for three times, drying the sample, and calcining the sample in a muffle furnace at 550-580 ℃ for 4-5h to obtain cobalt and lanthanum codoped modified silicon-aluminum-based molecular sieve powder;

s4: mixing the molecular sieve powder and boehmite according to a weight ratio of 5:0.1-1, adding a proper amount of polyvinyl alcohol or carboxymethyl cellulose, wetting with deionized water, tabletting and forming, fully drying at 110-120 ℃, crushing, sieving, selecting particles with the particle size of 0.1-0.5mm, and roasting at 550 ℃ for 3-5 hours to obtain a second catalyst of the formed molecular sieve;

s5: further, the molecular sieve prepared above is immersed in 2-3 wt% nickel nitrate solution in equal volume for 2-5h at room temperature, and then heated to remove water and fully dried, and then the dried solid is calcined again: firstly calcining at 400-450 ℃ for 2h, then cooling to room temperature, then continuously calcining at 350-360 ℃ for 1-2h under hydrogen atmosphere, and naturally cooling to room temperature to prepare the second catalyst containing the nickel-loaded molecular sieve.

5. Use of the composite catalyst according to any one of claims 1 or 2 in the preparation of amines by catalytic hydrogenation of nitrile feedstocks.

6. A method for preparing 2-methyl pentanediamine by hydrogenating 2-methyl glutaronitrile by using the composite catalyst of any one of claims 1 or 2, which is characterized in that 2-methyl pentanediamine is prepared by catalyzing the hydrogenation reaction of 2-methyl glutaronitrile in a high-pressure reactor containing an alcohol solvent and the composite catalyst at the temperature of 80-120 ℃ and in the presence of low content of ammonia; wherein the alcohol solvent is selected from methanol or ethanol, and the low content ammonia refers to the content of ammonia in the solution which is less than 0.5 wt%.

7. The method of claim 6, comprising the steps of:

adding an alcohol solvent and the purified raw material 2-methylglutaronitrile into a high-pressure reaction kettle, uniformly stirring, and then dropwise adding 20-30 wt% of ammonia water solution to ensure that the ammonia content in the solution is 0.1-0.5 wt%; then adding the composite catalyst to 1-10 wt%; replacing the internal atmosphere of the reaction kettle with hydrogen, and stirring and reacting at the hydrogen pressure of 0.5-3MPa and the reaction temperature of 80-120 ℃ to stop absorbing hydrogen as a reaction end point.

8. The method of claim 6, wherein the hydrogen pressure is 0.5 to 2MPa and the selectivity of the product 2-methylpentanediamine is not less than 80%.